In many parts of the world due to inadequate rainfall it is necessary at some times during the year to artificially water turf and landscaping. Residential and commercial irrigation systems typically include one or more solenoid operated valves that are turned ON and OFF by an electronic irrigation controller. The valves admit water to various subterranean branch lines usually made of PVC pipe that typically have several sprinklers connected to risers coupled to the branch lines at spaced intervals. Each combination of a solenoid valve and its associated sprinklers is referred to in the irrigation industry as a zone or station. A modern electronic irrigation controller typically includes a microprocessor and separate memory, or a micro-computer with on-chip memory, that stores and executes one or more watering programs. The watering programs can be pre-programmed by the user via push button and/or rotary controls. The controller usually has an LCD or other display to facilitate programming by the user. The microprocessor controls the solenoid valves via suitable drivers and switching devices. The valves are opened and closed by the microprocessor in accordance with the pre-programmed run and cycle times for each of the stations. The goal is to uniformly distribute the optimum amount of water over a given area.
Modular expandable irrigation controllers have gained increasing popularity in both residential and commercial landscape environments. In these controllers, the base portion of the system contains the microprocessor and user actuated controls. Each station is then controlled by a corresponding station module which comprises a plastic housing that encloses and supports a station module circuit, as well as wire connection terminals for connecting wires to a plurality of solenoid actuated valves. Typically each station module can independently control more than one solenoid actuated valve, i.e., station. The station modules contain pins, sockets, card edge connectors or some other standard form of electromechanical connectors for allowing them to be inserted into slots or receptacles in either the housing that contains the microprocessor or a separate back panel hinged to the microprocessor housing. The advantage of this configuration is that the controller need only be equipped with the minimum number of station modules that can control the total number of stations. Thus, for example, an irrigation system may have only three zones, requiring only a single station module, while another may have twelve stations which might require four station modules. Considerable cost savings are thus achieved. Moreover, if an irrigation system expands after initial installation because the landscaping has increased, additional station modules can be added.
A modular irrigation controller is typically connected to each solenoid actuated valve by a dedicated field valve line, for example, twelve gauge wire. A common return line is connected between all of the valves and the controller. Triacs in the station module circuit are used to switch a twenty-four volt AC signal ON and OFF each relative to each of the field valve lines. In conventional modular irrigation controllers, the stripped ends of the field valve lines are connected to screw type terminals or lever type terminals on the station modules themselves.
One of the drawbacks of conventional modular irrigation controllers is that they are usually larger than non-modular irrigation controllers capable of controlling the same number of stations. Since all of the field valve lines must be separately connected to corresponding modules, the modules must be oriented so that their terminals are all readily accessible for connection of the field valve lines. This requirement in turn prevents the modules from being stacked to reduce the overall size of the irrigation controller.
Another downside to conventional modular irrigation controllers involves the installation and connection of the field valve lines. Often contractors run spare field valve lines for later expansion of the irrigation system, but since the extra station modules will not be inserted into the controller until a later date, there are no terminals for the extra field valve lines. This can lead to mis-connection of extra field valve lines at a later date. If not properly labeled, it can be tedious to determine the zones that the extra field valve lines control. Moreover if the extra field valve lines that are unconnected are stripped of insulation, they can cause shorts.
Another problem with conventional modular expandable irrigation controllers arises when a station module is damaged and therefore must be removed and replaced. The station module that needs to be removed is sometimes “covered” with existing field valve lines that must be displaced. Sliding or other movement required to remove a station module may be impaired by the field valve lines attached to the defective station module or adjacent station modules. Moreover, quite often the installer mistakenly re-connects the field valve lines to the wrong terminals of the new station module so that the different stations that are supposed to be controlled by the module either do not run at all, or they do not run with the correct cycle and run times.